Rigid, conjugated and shaped arylethynes as mediators for the assembly of gold nanoparticles

The ability to control and tailor the interparticle structures and properties of molecularly-mediated assembly of nanoparticles in terms of molecular size, shape, and structure is essential for exploring the nanostructured multifunctional properties. This report describes the results of an investigation on how such molecular size, shape, and structure are operative in the assembly of gold nanoparticles mediated by rigid methylthio arylethynes (MTAs) of different shapes (e.g., I, V, Y, and X shapes). The goal of this investigation focuses on understanding the correlation between the interparticle molecular structures and the optical and spectroscopic (e.g., surface-enhanced Raman scattering (SERS)) properties in this class of molecularly-mediated assembly of nanoparticles. The surface plasmon resonance bands of the nanoparticles, the electronic transition bands of the mediator molecules, the dynamic light scattering of the assembly processes, and the SERS signatures of the interparticle structures are systematically compared for a series of MTAs. Important insights have been gained into the relative binding strength of the different MTAs in the single- and two-component mediated assembly processes. The results have demonstrated that the interparticle spacing and structures of nanoparticle assemblies can be defined by these rigid and shaped molecules. This type of interparticle structural definition can be controlled to produce well-defined optical and spectroscopic signatures, which is especially important for understanding interparticle optical or spectroscopic characteristics (e.g., "hot-spot" in nanoparticle-based SERS effect). Implications of the findings to enabling the design of interparticle structure and the control of the interparticle properties in nanoparticle assembly systems for potential applications in chemical/bio sensing, spectroscopic signal amplification, and microelectronics are also briefly discussed.